Question

which position vs time graph shows an object moving at a constant velocity in a positive direction?

Explanation:

Step1: Recall velocity - position - time relation

Velocity $v=\frac{\Delta x}{\Delta t}$, for constant velocity, the position - time graph should be a straight - line.

Step2: Analyze positive direction

For motion in the positive direction, the position $x$ should increase as time $t$ increases. A straight - line with a positive slope represents an object moving at a constant velocity in the positive direction.

Answer:

The graph with a straight - line having a positive slope (assuming one of the given graphs has this characteristic). Without seeing the actual graphs, we can't specify which number (1, 2, 3, or 4) it is. But the correct graph is the one that is a straight - line with a positive slope.